1. Field of the Invention
The present invention relates to a lithographic apparatus, a device manufacturing method and an apparatus for processing an exchangeable object.
2. Description of the Related Art
A lithographic apparatus is a machine that applies a desired pattern onto a target portion of a substrate. Lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In that circumstance, a patterning device, such as a mask, may be used to generate a circuit pattern corresponding to an individual layer of the IC, and this pattern can be imaged onto a target portion (e.g. including part of, one or several dies) on a substrate (e.g. a silicon wafer) that has a layer of radiation-sensitive material (resist). In general, a single substrate will contain a network of adjacent target portions that are successively exposed. Conventional lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing an entire pattern onto the target portion at once, and so-called scanners, in which each target portion is irradiated by scanning the pattern through the projection beam in a given direction (the “scanning”-direction) while synchronously scanning the substrate parallel or anti-parallel to this direction.
In a conventional lithographic apparatus a robot is used to exchange an exchangeable object. Examples of such exchangeable objects are substrates, which are exchanged for subsequent illumination, and patterning devices or masks which are exchanged for providing different patterns when illuminating the substrates.
A conventional robot generally includes a base part which is connected with usually a stationary part of the lithographic apparatus, and a movable part which may include a number of arms which are interlinked. A proximal end of the movable part is movably connected to the base part. On a distal end of the movable part, an object handler for holding an exchangeable object, for instance a substrate, is arranged.
The lithographic apparatus generally includes a sensor which is arranged on the object handler and which can detect the presence of an object in the object handler. It is desirable to detect the presence of an object in the object handler to make sure that the objects are handled properly. With the use of a signal provided by the sensor, it is possible, for example, to check that there is no object present in the object handler before a new object is taken by the object handler. In this way damage to the objects may be avoided.
In a conventional robot of the above-mentioned type, cabling is routed from the base part to the object handler to energize the sensor and to connect the sensor to a computer or such device to process the signal. The cabling is usually guided along the arms of the robot in order to avoid that the cabling can become caught between moving parts of the robot or other parts of the lithographic apparatus. As a result of the cabling being guided along the arms of the robot, the freedom of movement, e.g. a rotation, of the robot is limited. Additionally, the movement of the cables may cause particle generation near the exchangeable object, which in general is undesired.
Moreover, when the robot is used in a process chamber where a certain process environment is kept, for example, a vacuum chamber, the use of cabling in the process chamber leads to a number of further difficulties. The presence of cabling in the process environment may lead to outgassing of the cabling material and can have an undesired influence on the temperature in the process environment. Further, the feed-through of the cabling through the wall of the process chamber makes it necessary to provide a sealing for this feed-through.